Loss of engine heat energy from internal combustion engines has long been an issue for designers of engines and engine exhaust systems. Numerous efforts have been made to reduce and/or capture at least a portion of such energy losses, in many cases with varying degrees of success.
Some energy recovery systems have utilized Rankine cycles, employing fluids adapted to accommodate thermal energy transfers between boiler and condenser units. Other energy recovery systems have utilized dual fluids in more complex systems, typically involving parallel closed systems for accommodating transfers of heat energy between fluids, such as an engine coolant on one side, and steam energy generated by engine exhaust on the other, to power auxiliary units associated with a work machine, or to, in combination with brake systems for example, to convert heat-derived energy into battery power. The latter systems have typically involved hybrid machines that employ engines in combination with batteries for purposes of supplying dual motive power to the machine.
Although most of the above described energy recovery systems have been successful in capturing and converting thermal energy into electrical power, for example for restoring energy into batteries, none of such systems have employed capabilities for the transient storage and use of purely mechanical energy. Mechanical to mechanical transfer capabilities may be particularly useful for off-road machines requiring transient mechanical energy resources, such as for hydraulic systems employed to lift heavy loads, for power take-off units, or for other occasional workload demands not practically met by current and/or traditional electrical power sources.